And the current El Nino is certainly an odd bird. According to reports from NOAA and the National Weather Service, the center of highest sea surface temperatures for the El Nino this year is offset westward — coming closer to the date line than it typically does. This is a weird heat disposition for El Nino which is, at least, a mid ocean event and often pushes warming well across the Pacific to South American shores.

(Pacific sea surface temperature anomaly [SSTA]. Note the hot water pools off both Australia and North America. These zones are joined by a vast blanket of warmer than average waters arranged diagonally across the Pacific from SW to NE. This disposition includes the warm anomaly along the Equator which is hot enough to reach weak El Nino status. But the disposition of sea surface temperatures throughout the Pacific, with highest equatorial anomalies near the date line and warmer spikes near Australia and the North American West Coast is unusual. SSTA graphic provided by Earth Nullschool. Data Source: Global Forecast System Model and NCEP.)

It’s also late in coming, as typical El Ninos have tended to arrive in full form during late fall or early winter. A Christmas-time warming of waters off the West Coast of South America was a traditional call-sign for El Nino and one that resulted in its name — which is Spanish for “The Christ Child.” Late winter and early spring are more typical times for the formation of deeper warmer water that may trigger an El Nino later in the year but often do not herald a fully-developed event (see What is El Nino? for more related information).

For earlier this week strong westerly winds began to roar against the typical flow of the trades along the Equator. The west wind back-bursts (WWB) push warmer West Pacific waters eastward and downward, enhancing the sea surface temperature anomaly spikes that fuel El Nino.

As of early Wednesday, March 11, these west winds had formed a gale force wall stretching just past the date line from about 5 North Latitude to 10 South Latitude. A gale driven by parallel cyclones — a weaker system to the north (Bavi) and the newly gathering Pam, which may challenge south Pacific records as the strongest storm ever to form in that region. In the above graphic we see a related ten minute sustained WWB of a rather extraordinary 85 kilometers per hour (about 50 mph) along the 7.45 degree South Latitude line.

Strengthening Kelvin Wave in a Record Warm World

Just before the formation of these strong westerlies, sub-surface temperatures also began to spike. A warm Kelvin wave that had already started its run beneath the sea surface, as of March 4, was beginning to show signs of strengthening well in advance of the added shove coming from the vigorous WWB shown above.

Peak temperatures in the wave as of a week ago had hit more than +6 C above average. A heat signature that is starting to look, more and more, like the very powerful Kelvin Wave of early 2014 that belched so much warmth into the atmosphere and likely contributed to both the current strongly positive PDO as well as 2014’s new record high temperatures.

(Sea surface temperature signature of an El Nino Modoki, which is closer to what we are seeing now, even if the higher temperature levels are currently shifted more toward the Date Line. Image source: Japan Agency for Marine-Earth Science.)

During recent years, some scientific reports have indicated that Central Pacific Warming or El Nino Modoki will be more prevalent as a result of human-caused climate change. Study authors Tong Lee and Michael J McPhaden, in the 2010 paper entitled Increasing Intensity of El Nino in the Central Equatorial Pacific note that increases in Pacific Ocean temperatures are primarily expressed through more intense warming of the central regions:

Satellite observations suggest that the intensity of El Niño events in the central equatorial Pacific (CP) has almost doubled in the past three decades, with the strongest warming occurring in 2009–10. This is related to the increasing intensity as well as occurrence frequency of the so-called CP El Niño events since the 1990s. While sea surface temperature (SST) in the CP region during El Niño years has been increasing, those during neutral and La Niña years have not. Therefore, the well-documented warming trend of the warm pool in the CP region is primarily a result of more intense El Niño events rather than a general rise of background SST.

If so, it seems possible that global warming may well be influencing the rather strange El Nino evolution we are witnessing now.

In any case, Central Pacific Warming El Ninos have a somewhat different impact than Eastern Pacific Warming El Ninos. For one, they tend to ramp up, rather than cool down North Atlantic Hurricanes. They also tend to result in more, not less, drought for the US West Coast. For India, mid-ocean warming of the kind we are seeing now can result in an enhanced disruption of the Asian monsoon — kicking off drought and related food security risks.

Tong Lee and Michael J McPhaden continue by adding:

…. the amplitude of this new type of El Niño has increased in recent decades (Lee and McPhaden 2010). For convenience, hereinafter we refer this new type of El Niño as to CP warming (CPW). Compared with the canonical EPW, the CPW exhibits distinctly different impacts on worldwide climate. For example, the CPW shifts the anomalous convection westward and usually forms two anomalous Walker circulations in the tropical Pacific (Ashok et al. 2007; Weng et al. 2007; Weng et al. 2009). The westward displaced convection was suggested to be more effective in causing Indian drought (Kumar et al. 2006). The CPW increases hurricane frequency both in the Atlantic Ocean (Kim et al. 2009) and western North Pacific (Chen and Tam 2010), and also shifts tropical cyclone tracks in the western North Pacific (Hong et al. 2011).